Correlation unit

ABSTRACT

A photogrammetric system for automatically registering a pair of photographic images for stereographic inspection. Automatic registration of the photographic images is accomplished by electronically sensing parallaxes between the images, and by transforming the images to accomplish registration. Each of a pair of stereo photographs is scanned in X and Y by a separate flying spot scanner which is driven by X- and Y-raster generators. The output of the flying spot scanners is applied to a separate video processor for controlling and enhancing the image signals and then to a separate cathode-ray tube which is driven in X and Y by the same X- and Y-raster generators. The two cathode-ray tubes comprise the left and right sides of a binocular viewer. The output of each of the flying spot scanners and the X- and Y-raster signals are applied to a correlation system which detects parallax errors and first and second order distortions between corresponding sections of each of the photographic images. The correlation system divides the output signals of the flying spot scanners into different frequency band-pass regions for separate correlation of the components of each of the signals in each band-pass region. The output of the correlation system is applied, via a transformation system, as correction signals to the raster signals driving the flying spot scanners which enables the pair of photographic images to be viewed in registration.

United States Patent Hobrough [54] CORRELATION UNIT [72] Inventor:Gilbert L. Hobrough, Los Altos, Calif.

[73] Assignee: ltek Corporation, Lexington, Mass.

[22] Filed: Sept. 30, 1968 [21] Appl. No.: 822,085

Related US. Application Data [62] Division of Ser. No. 394,502, Sept. 4,1964, Pat. No.

[52] U.S.Cl ..235/181,328/109, 328/133, 324/83 D [51] Int. Cl ..G06g7/19, H03d 13/00 [58] 235/181; 179/15;250/220SP; 328/114, 133, 155, 109,110; 307/232 [56] References Cited UNITED STATES PATENTS 3,185,9575/1965 3,185,958 5/1965 3,197,625 7/1965 3,364,311 H1968 3,404,26110/1968 Jespers et al ..235/1 81 1 Feb.29, 1972 Primary Examiner-EugeneG. Botz Assistant Examiner-Felix D. Gruber Attorneyl-lomer 0. Blair andRobert L. Nathans [57] ABSTRACT A photogrammetric system forautomatically registering a pair of photographic images forstereographic inspection. Automatic registration of the photographicimages is accomplished by electronically sensing parallaxes between theimages, and by transforming the images to accomplish registration. Eachof a pair of stereo photographs is scanned in X and Y by a separateflying spot scanner which is driven by X- and Y-raster generators. Theoutput of the flying spot scanners is applied to a separate videoprocessor for controlling and enhancing the image signals and then to aseparate cathode-ray tube which is driven in X and Y by the same X- andY-raster generators. The two cathode-ray tubes comprise the left andright sides of a binocular viewer. The output of each of the flying spotscanners and the X- and Y-raster signals are applied to a correlationsystem which detects parallax errors and first and second orderdistortions between corresponding sections of each of the photographicimages. The correlation system divides the output signals of the flyingspot scanners into different frequency band-pass regions for separatecorrelation of the components of each of the signals in each band-passregion. The output of the correlation system is applied, via atransformation system, as correction signals to the raster signalsdriving the flying spot scanners which enables the pair of photographicimages to be viewed in registration.

12 Claims, 58 Drawing Figures PIG/ifllf/ON flldl 514N425 77:TINIIOIMlf/OM JYJfIM PAIENTEDFEBZS 1972 3,646,336

SHEET cu 0F 23 I NVENTOR. 6/; iii? 4 flaaiouwy PAIENTEDmzs I972 SHEETUSUF 23 I N V E NTOR. 6/4 an 1, #052004 PATENTEDFEB 29 1972 SHEET 110F23@MEQQX PATENTEDFEB29 I972 SHEET 12UF 23 PATENTEDFEBZQ I972 SHEET 13UF 23V w? wQww INVENTOR.

/wwew .4. Haaewa/v ham 1 PATENTEDFEBZS I972 3,846,336

sum 17 [1F 23 55$ ib k/ a INVENTOR.

1. A correlation system for operating upon first and second electricalinput signals generated from first and second data sources by an X- anda Y-scanning signal comprising: a. phase detection means, responsive tosaid first and second electrical input signals, for detecting phasedifferences between said first and second input signals, and forproducing an output signal indicative of said phase differences; b.first analyzer means, responsive said output signal and said X-scanningsignal, for producing an X-parallax error output signal; c. secondanalyzer means, responsive to said output signal and said Y-scanningsignal, for producing a Y-parallax error output signal; d. thirdanalyzer means, responsive to said X-parallax error output signal andsaid X-scanning signal, for producing an Xscale error output signal; ande. fourth analyzer means, responsive to said Y-parallax error outputsignal and said Y-scanning signal, for producing a Yscale error outputsignal.
 2. The system as set forth in claim 1 and further including: a.fifth analyzer means, responsive to said X-parallax error signal andsaid Y-scanning signal, for producing an X-skew error output signal; andb. sixth analyzer means, responsive to said Y-parallax error signal andsaid X-scanning signal, for producing a Y-skew error output signal. 3.The system as set forth in claim 2 and further including: a. means,responsive to said X-scanning signal and said Y-scanning signal, toproduce a composite scanning signal; b. seventh analyzer means,responsive to said X-parallax error signal and said composite scanningsignal, for producing an XY in X error oUtput signal; and c. eighthanalyzer means, responsive to said Y-parallax error signal and saidcomposite scanning signal, for producing an XY in Y error output signal.4. The system as set forth in claim 3 and further including: a. meansfor modifying said X-scanning signal to produce a modified X-scanningsignal having a frequency twice that of said X-scanning signal; b. meansfor modifying said Y-scanning signal to produce a modified Y-scanningsignal having a frequency twice that of said Y-scanning signal; c. ninthanalyzer means, responsive to said X-parallax error signal and saidmodified X-scanning signal, for producing an X2 in X error outputsignal; d. tenth analyzer means, responsive to said X-parallax errorsignal and said modified Y-scanning signal, for producing a Y2 in Xerror output signal; e. eleventh analyzer means, responsive to saidY-parallax error signal and said modified Y-scanning signal, forproducing a Y2 in Y error output signal; and f. twelfth analyzer means,responsive to said Y-parallax error signal and said modified X-scanningsignal, for producing an X2 in Y error output signal.
 5. A correlationsystem for operating upon first and second electrical input signalsgenerated from first and second data sources by an X- and a Y-scanningsignal comprising: a. phase detection means, responsive to said firstand second electrical input signals, for detecting phase differencesbetween said first and second input signals, and for producing an outputsignal indicative of said phase differences; b. first analyzer means,responsive to said output signal and said X-scanning signal, forproducing an X-parallax error output signal; c. second analyzer means,responsive to said output signal and said Y-scanning signal, forproducing a Y-parallax error output signal; d. third analyzer means,responsive to said X-parallax error signal and said Y-scanning signal,for producing an X-skew error output signal; and e. fourth analyzermeans, responsive to said Y-parallax error signal and said X-scanningsignal, for producing a Y-skew error output signal.
 6. A correlationsystem for correlating first and second electrical input signals andincluding: a. a first band-pass circuit connected to said first inputsignal for passing frequency components of said first input signalwithin the band-pass region of that channel; b. a second band-passcircuit connected to said second input signal for passing frequencycomponents of said second input signal within the band-pass region ofthat channel, said frequency components passed by said second band-passcircuit being in a band-pass region which includes at least a portion ofthe band-pass region in which said frequency components passed by saidfirst band-pass circuit are located; c. phase detection means fordetecting phase differences between the signals passed by said first andsecond band-pass circuits and for producing an output signal indicativeof said phase differences, whereby said output signal is representativeof correlation differences between said first and second electricalinput signals.
 7. The system as set forth in claim 6 wherein said firstand second electrical input signals are generated from first and seconddata sources by an x- and a y-scanning signal and wherein: a. eachelectronic channel further includes, first analyzer means, responsive tosaid output signal and said X-scanning signal, for producing anX-parallax error output signal, and second analyzer means, responsive tosaid output signal and said Y-scanning signal, for producing aY-paraLlax error signal; and b. said correlation system furtherincludes, means, connected to said X-parallax error output signalproducing means in each of said electronic channels, for combining theX-parallax error output signals and producing a composite X-parallaxerror output signal, and means, connected to said Y-parallax erroroutput signal producing means in each of said electronic channels, forcombining the Y-parallax error output signals and producing a compositeY-parallax error output signal.
 8. The system as set forth in claim 7wherein: a. each electronic channel further includes, third analyzermeans, responsive to said X-parallax error output signal and saidX-scanning signal, for producing an X-scale error output signal, andfourth analyzer means, responsive to said Y-parallax error output signaland said Y-scanning signal, for producing a Y-scale error output signal;and b. said correlation system includes, means, connected to saidX-scale error output signal producing means in each of said electronicchannels, for combining the X-scale error output signals and producing acomposite X-scale error output signal, and means, connected to saidY-scale error output signal producing means in each of said electronicchannels, for combining the Y-scale error output signals producing acomposite Y-scale error output signal.
 9. The system as set forth inclaim 8 wherein: a. each electronic channel further includes, fifthanalyzer means, responsive to said X-parallax error signal and saidY-scanning signal, for producing an X-skew error output signal, andsixth analyzer means, responsive to said Y-parallax error signal andsaid X-scanning signal, for producing a Y-skew error output signal; andb. said correlation system further includes, means, connected to saidX-skew error output signal producing means in each of said electronicchannels, for combining the X-skew error output signals and producing acomposite X-skew error output signal, and
 10. connected to said Y-skewerror output signal producing means in each of said electronic channels,for combining the Y-skew error output signals and producing a compositeY-skew error output signal.
 10. The system as set forth in claim 9wherein: a. each electronic channel further includes, means, responsiveto said X-reference signal and said Y-reference signal, to produce acomposite scanning signal, seventh analyzer means, responsive to saidX-parallax error signal and said composite scanning signal, forproducing an XY in X error output signal, eighth analyzing means,responsive to said Y-parallax error signal and said composite scanningsignal, for producing an XY in Y error output signal; and b. saidcorrelation system further includes, means, connected to said XY in Xerror output signal producing means in each of said electronic channels,for combining the XY in X error output signals and producing a compositeXY in X error output signal, and means, connected to said XY in Y erroroutput signal producing means in each of said electronic channels, forcombining the XY in Y error output signals and producing a composite XYin Y error output signal.
 11. The system as set forth in claim 10wherein: a. each electronic channel further includes, means formodifying said X-scanning signal to produce a modified X-scanning signalhaving a frequency twice that of said X-scanning signal, means formodifying said Y-scanning signal to produce a modified Y-scanNing signalhaving a frequency twice that of said Y-scanning signal, ninth analyzermeans, responsive to said X-parallax error signal and said modifiedX-scanning signal, for producing an X2 in X error output signal, tenthanalyzer means, responsive to said X-parallax error signal and saidmodified Y-scanning signal, for producing a Y2 in X output signal,eleventh analyzer means, responsive to said Y-parallax error signal andsaid modified Y-scanning signal, for producing a Y2 in Y error outputsignal, twelfth analyzer means, responsive to said Y-parallax errorsignal and said modified X-scanning signal, for producing an X2 in Yerror output signal; and b. said correlation system further includes,means, connected to said X2 in X error output signal producing means ineach of said electronic channels, for combining the X2 in X error outputsignals and producing a composite X2 in X error output signal, means,connected to said Y2 in X error output signal producing means in each ofsaid electronic channels, for combining the Y2 in X error output signalsand producing a composite Y2 in X error output signal, means, connectedto said Y2 in Y error output signal producing means in each of saidelectronic channels, for combining the Y2 in Y error output signals andproducing a composite Y2 in Y error output signal, and means, connectedto said X2 in Y error output signal producing means in each of saidelectronic channels, for combining the X2 in Y error output signals andproducing a composite X2 in Y error output signal.
 12. The system as setforth in claim 7 wherein: a. each electronic channel further includes,third analyzer means, responsive to said X-parallax error signal andsaid Y-scanning signal, for producing an X-skew error output signal, andfourth analyzer means, responsive to said Y-parallax error signal andsaid X-scanning signal, for producing a Y-skew error output signal; andb. said correlation system further includes, means, connected to saidX-skew error output signal producing means in each of said electronicchannels, for combining the X-skew error output signals and producing acomposite X-skew error output signal, and means, connected to saidY-skew error output signal producing means in each of said electronicchannels, for combining the Y-skew error output signals and producingcomposite Y-skew error output signals.